1. Field of the Invention
The present invention relates to a microwave oven, and more particularly, to a heating apparatus of a microwave oven for supplying a heat source other than microwave to a cooking chamber.
2. Description of the Background Art
In general, the microwave oven generates microwaves by using electricity. As the microwaves infiltrate into a cooking object, a movement of molecules is made in the cooking object, according to which the food stuff is heated.
In a case of currently used microwave ovens, since there is a limitations to use of only microwaves as a heat source for heating foodstuff, a heating apparatus is additionally installed to heat foodstuff by using a heating source other than microwaves.
FIG. 1 is a view showing the construction of a microwave oven having a heat apparatus in accordance with conventional art.
The conventional microwave oven includes: a cooking chamber 102 for receiving a cooking object; a tray 104 installed at a lower portion of the cooking chamber 102, being rotated with foodstuff placed thereon; a magnetron (not shown) mounted at one side of the cooking chamber 102, for generating microwaves for heating foodstuff; and a heating apparatus for providing a heat source required for heating foodstuff by a means other than microwaves generated from the magnetron.
Since there are various kinds of cooking objects to be cooked, the heating apparatus includes a first heating system for providing convection heat and a second heating system for providing radiant heat, to provide heat energy suitable to the kind or the property of the cooking object.
The first heating system includes a convection heater 106 disposed at a rear side of the cooking chamber 102, and heating air; and a ventilating fan 108 disposed at the center of the convection heater 106 and circulating the air inside the cooking chamber 102 to pass the convection heater 106.
A suction hole 112 for sucking air inside the cooking chamber 102 and a discharge hole 114 for supplying the air that is heated while passing through the convection heater 106 into the cooking chamber, are formed at the rear side 110 of the cooking chamber 102.
In the first heating system, when the ventilating fan 108 is driven, the air of the cooking chamber is sucked through the suction hole 112, and the sucked air is heated while passing through the convection heater 106 and again supplied into the cooking chamber 102 through the discharge hole 114.
The second heating system includes a grill heater 118 disposed at certain intervals at the upper portion of the cooking chamber 102, for generating radiant heat to directly heat the cooking object.
As stated above, as for the heating apparatus of a microwave oven in accordance with the conventional art, the first heating system is operated when convection heat is required according to the kind and the property of the cooking object to be cooked. That is, when the ventilating fan 108 is driven, air is circulated in the horizontal direction of the cooking chamber as indicated in the arrows xe2x80x98Axe2x80x99 as shown in FIG. 1, heating the cooking object.
Meanwhile, in case radiant heat is required, the cooking object is heated by a radiant heat generated from the grill heater 118 mounted at the upper portion of the cooking chamber.
However, the conventional heating apparatus of microwave oven has the following problems.
That is, since the first heating system for generating a convection heat and the second heating system for generating the radiant heat are separately mounted at the rear side and the upper portion of the cooking chamber, the installation space is much occupied, enlarging the size of the whole system, and since additional components are required, its production cost is increased according to the increase in the number of components.
In addition, since the radiant heat of the grill heater is circulated in the horizontal direction of the cooking chamber, heat transmittance to the cooking object is not desirable, resulting in degradation of heat efficiency, and accordingly, the cooking quality of foodstuff is degraded and the cooking speed is slow.
Therefore, an object of the present invention is to provide a heating apparatus of a microwave oven that is capable of reducing the size of a system by considerably reducing installation space by integrating a heating system for generating radiant heat and a heating system for generating convection heat and installing it at the upper portion of a cooking chamber, and capable of reducing production cost by reducing the number of components.
Another object of the present invention is to provide a heating apparatus of a microwave oven that is capable of improving heat efficiency as air is circulated vertically from the center of a cooking chamber in a case of using radiant heat, and capable of improving cooking quality of a cooking object and shortening the cooking speed by evenly transmitting heat to the cooking object.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described herein, there is provided a heating apparatus of a microwave oven including: an upper plate installed at an upper portion of a cooking chamber into which a cooking object is to be received, having a suction hole for sucking air inside the cooking chamber and a discharge hole for discharging air; a first heater installed at the discharge hole side of the upper plate, for generating convection heat; a second heater disposed in the same space as that of the first heater, for generating a radiant heat; and a ventilating fan installed at an upper portion of a region where the suction hole of the upper plate is formed, for circulating air inside the cooking chamber through the first and the second heaters.
The heating apparatus of a microwave oven of the present invention further includes an air guide fixed to cover the ventilating fan and the first and the second heaters at the upper side of the upper plate, for guiding air flow from the ventilating fan to the first and the second heaters.
The heating apparatus of a microwave oven of the present invention further includes a heater housing in which the first and the second heater are inserted and an air passage is formed at its upper side to supply air from the ventilating fan to the first and the second heaters.
In the heating apparatus of a microwave oven of the present invention, both ends of the first heater are fixed at the heater housing, and the first heater is formed in a bar type bent for several times to enlarge the area within which air passes.
In the heating apparatus of a microwave oven of the present invention, the second heater is disposed at the upper side of the first heater with a certain distance therebetween, of which both ends are fixed at the heater housing.
The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.